In the field of process automation technology, in many cases, field devices are used for registering and influencing process variables. Examples of field devices are temperature measuring devices, which register the temperature of a medium; flow rate meters, which register the flow rate of a medium in a section of piping; or fill level meters, which register the fill level of a liquid or bulk goods in a container.
Field devices are normally connected via a data or field bus with superordinated control units, e.g. process control systems PCS or an engineering system, from which the process activity is controlled or monitored, and also from which direct access to individual field devices is possible. As a result of the direct access to the field device, settings at the field device can be changed from the control unit, or diagnostic functions of the field device can be called up. In the control unit, the measurement values of the different sensors are evaluated or monitored, and, for process control, the appropriate actuators are activated. Data transfer between field device and control units is carried out according to known international standards for field buses, such as e.g. HART®, Foundation Fieldbus®, Profibus®, or CAN-Bus®, etc.
Frequently in process automation technology, field devices from different manufacturers are used. The servicing, or operating, of field devices is carried out by means of PC-based applications, which especially support the parameterization, start-up, and diagnostics of individual field devices, in part also graphically.
Examples for such display- and service-programs are AMS® of Fisher-Rosemount, Simatic PDM® of Siemens, Smart Vision® of ABB, WO® of Vega, or Commuwin® II of Endress+Hauser.
In order to enable the servicing of different field devices from a control unit, the functionality of the respective field device must be known to the control device. The functionality of the field device is described by means of a so-called device description (Device Descriptions DDs). For this, a special language, the device descriptions language, is available. By means of this standardized language, the necessary information concerning the functionality of a specific field device can be made available to other bus participants, especially the control system, or an additional service device (handheld device). Normally the device descriptions are created by the field device manufacturer, and are delivered with the respective field device e.g. on disk.
At the start-up of the field device, the appropriate device description is then installed from the application program.
This is problematic in that device descriptions are periodically updated by the manufacturer. The updated device descriptions (updates) must then be sent to the corresponding user, and are then subsequently installed manually using the application program.
In this procedure, it is not guaranteed that the user is, in fact, using the most recent update of the device description. Especially in the case of safety-related process applications, it is mandatory that the most recent data description is made available to the user, especially when programming errors (bugs fixing) have appeared in a version of a device description.